fix(core): revert Error cause arg — package TS lib is < ES2022 (unbreaks build)

The 2-arg `new Error(msg, { cause })` form needs ES2022 lib; this package
targets lower, so tsc failed TS2554 in the Bundle Analysis build. It was a
gratuitous fix for a non-CI-gated lint rule on pre-existing code — reverted to
the original single-arg throw. The #2661 CEL routing is unchanged.

Author: claude

packages/core/src/evaluator/ExpressionEvaluator.ts

@@ -169,7 +169,7 @@ export class ExpressionEvaluator {
       // Execute with context values
       return compiled.fn(...varValues);
     } catch (error) {
-      throw new Error(`Failed to evaluate expression "${expression}": ${(error as Error).message}`, { cause: error });
+      throw new Error(`Failed to evaluate expression "${expression}": ${(error as Error).message}`);
     }
   }